Telephone system



Dec. 22, 1931. I w 5 VICK ET AL 1;837,801

TELEPHONE SYSTEM Filed Nov. 21, 1928 2 Sheets-Sheet 1 Inua'n'i'u'FiLnjiniim 51 5i Uick Gen 5 Dan TuTl'Efi Dec. 22, 1931. w. s. VlCK ET AL7,

4 TELEPHONE SYSTEM Filed Nov. 21, 1928 2 Sheets-Sheet 2 lam-rd??? fWilliam SHIT 15 Uick Patented Dec. 22, 1931 NITED STATES PATENT oFFIcEWILLIAM STANLEY VICK AND GEORGE DEAN 'IJIJTR'ZII'ON, OF LIVERPOOL,ENGLAND, AS-

SIGNORS TO ASSOCIATED TELEPHONE .AND TELEGRAPH COMPANY, OF KANSAS CITY,

MISSOURI TELEPHONE SYSTEM Application filed November 21, 1928, SerialNo. 320,826, and in Great'IBr-itain December 9, 1927.

The present invention relates to automatic telephone systems and thougha number of its features are of more general application, it can beemployed to particular advantage in connection with small exchangescomprising comparatively few lines which are moreover all comparativelyshort. The main object of the invention is to reduce to a minimum theamount of equipment required in v a small exchange system, forinstance'an isolated unit such as is generally known as P. A. X. Thisobject is attained both by a reduction in the number of relays in theconnecting equipment itself and also by a simplification of thearrangements for transmitting signalling currents of Various kinds tothe subscribers to indicate particular stages in the connection.

According to one feature of the invention, in a system employing finderswitches and having subscribers lines provided with line relayspermanently connected thereto and an alternating current bell at thesubstation normally bridged across each line in series with a condenser,a wanted party is signalled by the intermittent short-circuiting of hisline which causes his bell to be rung by con denser discharge.

According to another feature of the inven-' tion in a system employingfinder switches and having subscribers lines provided only withindlvldual line relays which are permanently connected thereto thecircuit for starting up a finder due to the energization of the linerelay when the receiver is removed is rendered ineffective if the lineis seized over a connector for an incoming call.

A further feature of the invention is that in a system employing finderswitches and having subscribers lines provided with line relayspermanently connected thereto the continued operation of a finder switchis dependent upon the supply of guarding potential which is adapted tobe connected up over one wiper due to the unoperated condition of theline relay if the line is non-calling or over another wiper fromequipment temporarily associated with the line if it is already engagedin a completed connection. In order that the invention maybe fullyunderstood and readily carried into efi'ect, by way of example atelephone system embodying the principles of the invention will now bedescribed in detail with reference to the annexed drawings. Fig. 1 showsa subscribers line relay L, which is individual to the particularsubscriber, the connecting circuit CC with which is associated thefinder switch FS which extends the calling subscriber to the connectingcircuit CC, and the connector switch CS by means of which connections toa wanted subscriber are established. Fig. 2 shows the circuit of thedistributor or allotter D, and the relays BU, RY and RX and M, N, and P,for supplying respectively busy tone, ringing and time periods to theexchange. For a proper understanding of the circuits Fig. 2 should beplaced immediately below Fig. 1 with the corresponding conductors inalignment. It should be mentioned also that the substations are of thewellknown type having the bell normally connected across the line inseries with a condenser. The setting up of a shown willnowbe tracedthrough in detail. When the subscriber to whose instrument conductors 8and 9 extend lifts his receiver to originate a call, linerelay Loperates and at armature 1O earths the guarding conductor extending tothe banks of the connector switches such as GS, at armature 1 2 removesearth from the associated bank contacts of the finder switches such asFSand at armature 11 completes a circuit for relay DX over conductor 73,armature 78, conductor 60 and armature 20. Relay DX upon operating inthis circuit completes a holding circuit for itself at armature 76,closes a point in the circuit of magnet DM3 at armature 74 and atarmature 7 5 completes a circuit for relay DY which operates in serieswith the rotary magnet DM3, the magnet however not receiving suificientcurrent to energize it. Assuming the connecting circuit CC is idle atthis time and has been preselectedby the distributor D, earth is nowextended from armature 7 9 over wiper 83 and bank contact, conductor 62,lower winding of. relay A of the connecting circuit to battery. Relay Acall on the apparatus operates, and at armature 27 prepares the circuitof relay B and at armatures 29 and 80 extends the circuit of the finderswitch driving magnet DMl to wiper 65 and 64 respectively of the finderswitch. All contacts associated with non-calling lines in the bank ofwiper 64 are earthed and all contacts associated with lines engaged onestablished connections in the bank of wiper 65 are earthed, so that thedriving magnet will ad'- Vance the wipers until they encounter thecontacts associated with the calling line, relay B being held shunted bythe driving earth till the contacts to which no earth is connected arereached. Relay 3 then operates in series with the magnet, and atarmature 14 opens the homing circuit of-the switch CS, at armature 15prepares the impulsing circuit, at armatures 16 and 19 completes aholding circuit for itself, at armature 18 connects earth to wiper 65and bank contact of the finder switch and hence to armature 11 of .relayL and also to conductor 69 extending to the connector switch banks toguard the line from seizure by other calling subscribers, and atarmature 17 connects earth over wiper 49 in normal position and wiper 82to the left-hand terminal of relay DX. Relay DX is now shunted andreleases allowing relay DY to release. Relay DY however, is fitted witha copper slug and is therefore slow' to release, so that a momentarycircuit is completed from earth over armatures and 100 to the drivingmagnet DM3. This circuit is maintained during the releasing time ofrelay DY and when relay DY is fully restored is broken. The magnettherefore energizes momentarily and moves the wipers of the switch D tothe next set of contacts in readiness for the next call. \Vhen wiper 82advances the short-circuit on relay DX is removed so that if anotherline is calling at this time the next finder switch may be started up onthe re-energization of relays DX and DY.

Relay B moreover at armature 20 connects earth to the common conductor61 to start thebusy tone relay BU and the interrupter relays M, N and P.It will be seen that the busy tone relay BU breaks its own circuit atarmature 84, thus causing it to operate and release rapidly and byinduction producing in its other winding a tone which is used fordialling indication and busy signal. At this stage the tone is passedfrom the lower winding of relay BU over conductor 51 and first bankcontact and wiper 46 of the connector switch CS, condenser 102, armature24 to the calling subscribers lineover the talk condenser and wiper 68of the finder switch. The subscriber upon hearing the tone commences todial the required number.

It will be convenient at this stage to consider the action of theinterrupter relays M, N and P. The earth on common conductor 61 operatesrelay P'over armature 98 and relay P then operates relay N over armature99. and at armature 98 provides a locking circuit for itself. Relay Ncloses a holding circuit for itself at armature 96 and at armature 95completes the circuit for relay M to operate. Relay M locks itself up atarmature 92 and at armature 91 shunts relay P which releases after aslight interval and shunts relay N. Relay N in turn releasing after aninterval shunts relay M and the release of relay M in due course againcompletes the circuit for relay P when the above cycle is repeated. Asthe relays M, N and P are. all slow to operate and slow to release, thisoperation is continued with perfect regularity, and the circuitsrequiring to be interrupted periodically are taken as shown overcontacts of relays N and P.

Returning now to the operation of the connector circuit, when thesubscriber operates his calling device he intermittently breaks thecircuit of relay L which de-energizes cor respondingly. The subscribersnumbers are arranged from 1 to 9, 01 to 09, and 001 to 004 and it willbe assumed that a single figure number, say 2, is being called. Eachtime relay L restores an earth pulse is extended from armature 10, bankcontact and wiper 66 of the finder switch FS, armatures 15 and 26 to thedriving magnet DM2 of the connector switch and also over armature 25 tothe upper winding of relay A so as to hold relay A energized during thetrain of impulses. It will be noted that after the distributor hasstepped, and before impulsing has commenced, relay A is held from earth.armature 17, home position bank contact and wiper 49. of the connectorswitch, interrupter springs 44, lowerwinding of relay C, armature 28,wiper 48 and home position bank contact of connector switch, lowerwinding of relay A to battery. Relay C does not on crate in thiscircuit. The wipers of the connector switch OS are advanced inaccordance with the impulses from the calling device till they areresting on the contacts associated with the desired subscribers line.

- If the called subscriber is busy, earth will be encountered by wipers45 and 48 from the conductors 50 and 54 corresponding respectively toconductors 69 and 7 O of the calling subscribers line circuit and relayC is un able to operate as it is short-circuited. Belay A restores afterits slow releasing period and busy tone is now transmitted to thecalling subscriber from the busy tone relay BU over condenser 101,interrupter armature 9?, conductor 55, armatures 42, 35, 13 and 24, tothe subscribers line over the speech condenser and wiper 68 of thefinder switch. The sub- Assuming now that the Wanted subscriber T9 isfree, relay C will operate from earth on the homing plate and wiper 49,interrupter springs 44, lower winding of relay C, armature 22, wiper andbank contact to battery on conductor 50, which is the called subscribersequivalent of conductor 69. At armatures 31 and 36 respectively relay Ccompletes locking and control circuits for itself, at armature 32prepares a circuit for relay E and at armature 33 prepares a circuit forits second winding, both of the latter circuits becoming effective assoon as relay A releases and armatures 22 and 23 engage their backcontacts. Relay C moreover at armature 35 completes the ringing tonecircuit and at armature 38 connects earth to the common conductor 56whence it is extended over armature 94, which as described previouslyispulsing, armature 87, winding of relay RY to battery. Relay RY operateswhen its-circuit is closed and at armature operates relay RX whichbreaks the circuit of relay RY at armature 87. Relay RY releases andallows relay RX to release when the circuit of relay RY is againcompleted and the above sequence of operations will be repeated. It willbe seen there fore that due to the design of relays RX and RY there is acomparatively rapid inter-operation between these relays during the timethat relay N is operated and has closed its armature 94. The operationof relays C and E extended .the called subscribers line from wipers 46and 47 of the connector switch CS over armatures 40 and 43, armatures 34and 3?, conductors 59 and 58 to armature 86 of relay RX and the rapidoperations of relay RX cause the line to be short-circuitedintermittently. This causes the called subscribers line relay toenergizeand release rapidly and the resulting discharge from thecondenser in the called substation circuit operates the bell. Thisringing is divided up into suitable periods by the interrupting relay N,and an indication to the calling subscriber that rin ging is takingplace is provided over conductor 57 by way of condenser 103 andarmatures 35, 13 and 24. It will beunderstood that armatures 88, 89 and90 are associatedwiththe other connecting circuits such as CC andperform 3 functions similar to armature 86.

It has been mentioned that the short-circuit on the called subscribersline operates his line relay intermittently and this accordinglyconnects earth to the conductor 54, which corresponds to conductor 70.This earth shunts the subscribers to converse. The calling and calledsubscribers receive talking battery through'the windings-of theirrespective line relays, such as L for the calling subscriber, which arepermanently connected to the lines.

Earthis maintained on conductor 50 after relay C releases from armature17 over armatures 39, normally closedsprings controlled by armature 31and wiper 45, andon conductor 54 from contacts corresponding to 10 ofthe called subscribersline relay, thus preventing the calledsubsi-ribers-line being take by another calling party. During theringingof the called subscribers'bell, earth is connected to wiper 45through the upper low resistance j windin'gof relay C over armatures.33, 22 and 31 thus guarding the line during the ringing of the wantedsubscriber and preventing the starting up of a finder switch due to theoperation of the'line relay since the battery connection associated withthe armature such as armature 11 is thereby rendered ineffective forproducing the operation of the're-layDX. At the conclusion of theconversation, the

release of the equipment takes place when relay L of the callinglinerestores and extends earth from armature 12 over the bank contact andwiper 64 of the finder switch .to relay B,.thus shunting relay B andcausing it to release. The release of relay B removes earth from thecommon conductor 61 to allow the tone and interrupter relays to restore,opens the circuit of relay E at armature 17, and at armature 14completes the homing circuit for the driving magnet DM2 of the.connector switch. Earth on the homing plate is extended overwiper 49,interrupter springs 44, armatures :14 and 25, winding of the magnet DM2to battery and energizes the magnet which moves the wipers to homeposition where earth is no longer encountered and therefore no furtherrotation can take place. As long as the connector switch is oif-normalearth from the homing plate is extended to conductor 63 and this guardsthe connector'inthe distributor bank till the switch has reached itshome position.

It will be noticed that the earth to operate relay 'DX at thecommencement of a call is obtained from resting contacts 20 of the malays B of the connector circuits to the common conductor 60. Iftherefore, a subscriber endeavours to make a. call when all theconnector circuits are in use, he cannot operate relay DX and must thenwait until a connector circuit becomes free when he will receive dialtone as usual.

When a subscriber calls another subscriber who has a two or three figurenumber, the dialling of the initial digit 0 moves the connector switchten steps and it will be seen from the wiring of the bank 48 of theconnector switch that relay A is held operated over the eleventh contactin the bank of wiper 48, thus preventing relays C and E from switchingto start the ringing. The subscriber then dials the next digit and theconnector switch is advanced further and when it stops, unless the digitis O, relays C and E will operate and ring the wanted subscriber asalready described. It the second digit dialled is also'O, the connectorswitch again reaches a contact on which relay A is held and the diallingof the third digit then enables theavanted subscribers line to bereached. No subscribers lines are connected to contacts 11 and 21 of theconnector switch.

'What we claim as new and desire to se cure by Letters Patent is 1. In atelephone system, subscribers lines each having a line relay permanentlyconnected thereto, abell and a condenser normally bridged in seriesacross each line at the 'subscribers station, a connector having accessto saidli'nesand means for intermittently short-circuiting a line withwhich said connector is connected whereby the bell at the subscribersstation is rung by the dis charge of the associated condenser.

2. In a telephone system, a subscribers line, .a line relay permanentlyconnected thereto and energized on both incoming and outgoing calls,finder switches having access to said line, a start relay common to saidfinders, a circuit for said start relay closed by the energization ofsaid line relay, and means for rendering said circuit ineffective incase the line relay is energized due to an incoming call.

3. In atelephone system, a subscribers line, a line relay permanentlyconnected thereto and energized on both incoming and outgoing calls, astart relay, means for energizing said start relay when said line relayis operated on an outgoing call, and means for short-circuiting saidstart relay when said line relay is operated on an incoming call.

4. In a telephone system, a connector, a called line having a line relaypermanently connected thereto, means for operating said connector toseize said line, means including said relay for signalling thesubscriber on said line, means controlled by the connector for busyingsaid line during the signalling period, and means controlled by saidline relay for busying said line after the called subscriber hasanswered.

5. In a telephone system, subsc ibers lines, automatic switchingmechanism for enabling a calling line to be extended to a called line,means for signalling the called line, a circuit for guarding the calledline against seizure during the signalling period. and a second circuitfor guarding the called line against seizure after the called party hasanswered.

' 6. In a telephone system,a calling line and a called line, automaticswitching mechanism for enabling said calling line to establish aconnection to said called line, and two busy circuits for guarding thecalled line against seizure eiiective at different times after theconnection to the called line has been completed.

7. In a telephone system, subscribers lines, a finder switch havingaccess to said lines, means for starting said switch responsive to acall, a circuit completed over one wiper of said switch for causing theswitch to pass over lines which are not calling or being called, and asecond circuit completed over a second wiper of said switch for causingthe switch to pass over lines which are already engaged in a completedconnection.

8. In a telephone system, means for completing connections betweencalling and called lines, a battery, and a line relay associated witheach line through which current from said battery is supplied to theline for talking and signalling purposes.

9. In a telephone system, subscribers lines each having a line relaypermanently connected thereto, a plurality of line finders, a relay ineach of said finders, a distributor for preselecting an idle finder,means responsive to the initiation of a call over one of said lines iorenergizing the relay in thepreselected finder over a wiper of saiddistributor, means responsive to the operation of said relay foroperating said finder to'connect with the calling line, and means formaintaining said relay energized by impulses transmitted from the linerelay of the calling line over a wiper of said finder after the finderhas come to rest.

10. In a telephone system, subscribers lines each having a line relaypermanently connected thereto, a bell and a condenser normally'bridgedin series across each line at the subscribers station, a connectorhaving access to said lines, means for intermittently short-circu ting aline with which said connector is connected whereby the line relay ofsaid line .is intermittently operated and the bell at the subscribersstation is rung by the discharge of the associated condenser, a ringcontrol relay in said connector, and means controlled by said line relayfor s'hort-cir cuiting said ring control relay.

11. In a telephone system, subscribers lines, a finder switch havingaccess to said lines, means for starting said switch responsive to theinitiation of a call, and two test ing circuits extending over twoseparate wipers of said switch for causing said switch to pass overnon-calling lines, said circuits simultaneously testing for absence ofground potential.

12. In a telephone system, a subscribers line, a line relay associatedwith said line and energized on both incoming and outgoing calls,automatic switching apparatus, means for extending said line to saidautomatic switching apparatus when said line relay is energized on anout oing call, and means for rendering said first means ineffective incase said line relay is energized on an incoming call.

13. In a telephone system, subscribers lines, a finder switch havingaccess to said lines, means for starting said switch responsive to theinitiation of a call over one of said lines, a pair of talkingconductors in said switch, and two testing circuits extending over twoseparate wipers of said switch independent of said talking conductors,said testing circuits effective simultaneously to cause said switch topass over non-calling lines.

14. In a rotary hunting switch, an operating magnet, a relay, a circuitincluding said magnet and said relay in series, two test wipersconnected in multiple to said circuit at the junction between saidmagnet and said relay for intermittently operating said magnet andmaintaining a shunt around said relay as long as either of said wipersencounters ground potential, said relay operating in series with saidmagnet to stop said switch as soon as neither of said wipers encountersground potential.

In testimony whereof I, the said WILLIAM STANLEY VIoK have signed myname at Liverpool, England, this 26th day of October, 1928. r

WILLIAM STANLEY VICK.

In testimony whereof I, the said GEORGE DEAN TURTON have signed my nameat London, England, this 24th day of October, 1928.

GEO. DEAN TURTON.

